feat(stalwart): deploy Stalwart mail server with CNPG and S3

- stalwart namespace with Deployment + HPA (2-6 replicas)
- CNPG PostgreSQL cluster (3 instances, 20Gi cephrbd-fast-delete) with PgBouncer pooler
- S3/Ceph-RGW for blob storage (stalwart-maildata bucket, lz4 compressed)
- Secrets from Vault: postgres-credentials, s3-credentials, stalwart-admin
- TLS cert via cert-manager (vault-issuer) for mail.main.unkin.net
- SMTP relay on port 25 (internal ClusterIP, trusted pod CIDRs)
- Submission on port 587, IMAP 143/993, HTTPS 443 via LoadBalancer
- HTTP port 8080 for Traefik reverse proxy (web admin at mail.k8s.syd1.au.unkin.net)
- Outbound mail routed through postfix.mailgateway.svc.cluster.local:25
- Spam filtering offloaded to postfix/rspamd (disabled internally)

apps/base/stalwart/services.yaml

@@ -0,0 +1,54 @@
+---
+# Internal service - postfix connects here to deliver inbound mail
+apiVersion: v1
+kind: Service
+metadata:
+  name: stalwart
+  namespace: stalwart
+spec:
+  selector:
+    app: stalwart
+  ports:
+    - name: smtp-relay
+      port: 25
+      targetPort: 25
+      protocol: TCP
+    - name: http-internal
+      port: 8080
+      targetPort: 8080
+      protocol: TCP
+    - name: metrics
+      port: 9090
+      targetPort: 9090
+      protocol: TCP
+---
+# External LoadBalancer for user-facing mail services
+apiVersion: v1
+kind: Service
+metadata:
+  name: stalwart-external
+  namespace: stalwart
+  annotations:
+    external-dns.alpha.kubernetes.io/hostname: mail.main.unkin.net
+spec:
+  type: LoadBalancer
+  externalTrafficPolicy: Local
+  selector:
+    app: stalwart
+  ports:
+    - name: submission
+      port: 587
+      targetPort: 587
+      protocol: TCP
+    - name: imap
+      port: 143
+      targetPort: 143
+      protocol: TCP
+    - name: imaps
+      port: 993
+      targetPort: 993
+      protocol: TCP
+    - name: https
+      port: 443
+      targetPort: 443
+      protocol: TCP